1. Field
The present disclosure relates generally to the formation of composite structures and the formation of metallic bladders. More particularly, the present disclosure relates to thermoplastic composite structures. Yet more particularly, the present disclosure relates to a method and apparatus for forming a metallic bladder. Further, the present disclosure relates to a method and apparatus for consolidating a structure comprising a thermoplastic material.
2. Background
Composite materials may be tough, light-weight materials created by combining two or more functional components. For example, a composite material may include reinforcing fibers bound in a polymer resin matrix. Resins used in composite materials may include thermoplastic or thermoset resins. A thermoplastic material may become soft upon heating and may harden upon cooling. A thermoplastic material may be able to be repeatedly heated and cooled. A thermoset material may become hard when heated. The fibers may be unidirectional or may take the form of a woven cloth or fabric.
Currently, composite structures may be created using thermoset materials. However, the time required to create a structure from thermoset materials may be undesirable.
For example, the speed of placing thermoset composite materials may be limited. Further, curing a thermoset material may require several hours. In addition to holding the thermoset material at a curing temperature for several hours, conventional autoclaves using resistive heating to cure thermoset materials may further require several hours for heating up and cooling down.
Consolidating a thermoplastic material may take significantly less time than curing a thermoset material. However, the time for resistive heating during consolidation of thermoplastic material may still be undesirable.
Further, stamp forming of thermoplastic material may currently be used to form non-planar thermoplastic structures. Alternative methods to traditional stamp forming of thermoplastic material may be required to produce thermoplastic structures having non-planar structures, including structures having closed cross-sections. An alternative method of producing a thermoplastic structure may provide improved processing of ply drops, ply additions, and other features of the thermoplastic structure. Improved processing may include improve quality of the resulting thermoplastic structure.
Yet further, consolidation of thermoplastic materials may cause loss of definition of the thermoplastic material. Loss of definition may include loss or rounding of features of the thermoplastic material. Specifically, tooling for consolidation may include round features of the thermoplastic material. Features may include ply drop-offs, ply additions, ramp ups, ramp downs, or other changes in the number or locations of plies causing varying composite material thickness. Consolidation of a thermoplastic material with features causing varying composite thickness may cause rounding of these features.
Still further, reusable tooling for consolidation of thermoplastic materials may be desired. Tooling may have substantially the same shape as the thermoplastic material to be consolidated. Further, it may be desirable to increase the longevity of tooling for consolidation.
Accordingly, there is a need for a method and assembly for forming non-planar thermoplastic structures. Specifically, there is a need for a method and assembly for consolidating thermoplastic structures having closed cross-sections. Further, there is a need to consolidate the thermoplastic sandwich structures faster than using resistive heating. Yet further, there is a need to consolidate thermoplastic structures without loss of definition of features. Still further, there is a need for forming tooling for consolidation of thermoplastic structures and maintaining or increasing the longevity of the tooling. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.